GRASAS Y ACEITES 65 (1) January–March 2014, e010 ISSN-L: 0017-3495 doi: http://dx.doi.org/10.3989/gya.074113 Simultatenous determination of diacetyl and acetoin in traditional turkish butter stored in sheep’s rumen (Karinyagi) R. Gokcea, A. Akdoganb,*, U. Divriklibb and L. Elcib aPamukkale University, Faculty of Engineering, Food Engineering, 20017 Denizli-Turkey bPamukkale University, Science & Art Faculty, Department of Chemistry, 20017 Denizli-Turkey *Corresponding author: [email protected] Submitted: 8 July 2013; Accepted: 14 October 2013; Published on line: 13/02/2014 SUMMARY: Commercial Karinyagi (traditionally named karin) is made of cows’ milk cream and is produced by filling butter in cleaned sheep’s rumen. The effect of butter storage in sheep’s rumen on the production of diacetyl and acetoin was investigated. These compounds were determined by GC-MS and they are the typi- cal butter flavor commonly found in fermented dairy products. The modified method for the simultaneous extraction of diacetly and acetoin from butter samples was accurate and precise. The recoveries of diacetyl and acetoin were 94.7 and 110.8%, respectively, while the detection limits were 1.83 and 0.51 mg·L-1, respectively. The proposed method was applied for the monitoring of aroma compounds in Karin butter samples during dif- ferent time intervals. The concentration of acetoin remained stable through 0–50 days while the concentration of diacetyl increased to 33.0 µg·g-1 up to 40 days and remained constant through 40–50 days. KEYWORDS: Acetoin; Butter; Diacetyl; GC/MS RESUMEN: Determinación simultánea de diacetilo y acetoína en mantequilla tradicional turca (Karin) alma- cenada en el rumen de oveja. El Karinyagi comercial (nombre tradicional Karin) está hecho de crema de leche de vaca, y producido llenando con mantequilla el rumen limpio de ovejas. Se ha investigado el efecto del almace- namiento de la mantequilla en el rumen de ovejas sobre la formación de diacetilo y acetoína. Estos compuestos son el típico flavor a mantequilla que se detecta comúnmente en los productos lácteos fermentados y han sido determinados mediante GC-MS. El método modificado para la extracción simultánea de diacetilo y acetoína en mantequilla resultó ser exacto y preciso y las recuperaciones de 94,7 y 110,8 % respectivamente, mientras que los límites de detección fueron 1.83 y 0,51 mg·L-1, respectivamente. El método propuesto se aplicó al control de compuestos aromáticos en Karin y muestras de mantequilla, durante diferentes intervalos de tiempo. La con- centración de acetoína se mantuvo estable entre 0–50 días mientras que la concentración de diacetilo aumentó a 33,0 mg·g- 1 hasta 40 días y se mantuvo constante entre 40–50 días. PALABRAS CLAVE: Acetoína; Diacetil; GC/MS; Mantequilla Citation/Cómo citar este artículo: Gokce R, Akdogan A, Divriklib U, Elci L. 2014. Simultatenous determination of diacetyl and acetoin in traditional turkish butter stored in sheep’s rumen (Karinyagi). Grasas Aceites 65 (1): e010. doi: http://dx.doi.org/10.3989/gya.074113 Copyright: © 2014 CSIC. This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial (by-nc) Spain 3.0 Licence. 2 • R. Gokce, A. Akdogan, U. Divriklib and L. Elci 1. INTRODUCTION which is the final product of citrate metabolism by certain lactic acid bacteria such as Lactococcus lac- The production and consumption of fermented tis subsp. lactis biovar diacetylactis and Leuconostoc. milk products have been increasing throughout the Diacetyl is produced from the spontaneous oxida- world (Macciola et al., 2008). In Turkey, butter is man- tive decarboxylation of α-acetolactate which can ufactured from two different fermented milk prod- also be transformed into acetoin by α-acetolactate ucts, cream and yoghurt. Butters have been produced decarboxylase or by spontaneous non-oxidative industrially or traditionally by two different methods decarboxylation (Aymes et al., 1999; de Vos and (“yayik butter” and “karin butter”) for centuries in Hugenholtz, 2004; Leroy and De Vuyst, 2004; Singh Turkey. Industrial butter is packed with aluminum et al., 2006; Quintans et al., 2008; Mallia et al., 2008). foil, plastic or paper wrap and stored, whereas Karin The determination of diacetyl and acetoin by butter is stored in a goat or sheep’s rumen as a tradi- standard methods typically involves the use of pre- tional way in the Mediterranean and Aegean region of concentration by vacuum distillation, liquid–liquid Turkey. The use of the rumen of sheep and goat allows extraction, solid phase extraction and more recently, air and water vapor permeability during the storage of purge and trap techniques (Frank et al., 2004). dairy products such as butter and cheese, and is one of Recently, diacetyl in milk products has often been the oldest traditional preservation methods. determined by a headspace technique coupled with Karin butter is produced from the cream obtained gas chromatography, using flame-ionization or mass from the milk cream of cows. For this aim, creams spectrometer detectors (Adahchour et al., 1999; Frank containing 70 to 80% fat are kneaded in a vessel et al., 2004; Bartowsky and Henschke, 2004; Panseri with handles to remove any components except for et al., 2011). fat. During the kneading process, the brine formed is Several techniques such high-pressure liquid discharged from the system by a discharging canal at chromatography (HPLC), spectrophotometric, fluo- the bottom of the vessel. After the brine is removed rometric and capillary zone electrophoresis have been from the structure to a certain ratio, the butter in reported for the determination of diacetyl and acetoin the vessel is washed with tap water at 18–20 °C. The (Bartowsky and Henschke, 2004; Ligon et al., 2008). butter is salted so that the final product contains 2% To the best of our knowledge, there are no salt after washed at least three times until the brine reports on diacetyl and acetoin concentration in becomes clear. Kneading is continued for some time karin butter produced in a traditional way. Sheep to obtain a homogenized dispersion of the salt. When rumen is used as packing material for karin butter the kneading operation is complete, the butter is left protection which probably has some affects on the in cold storage for a night in blocks of 10 kg. The next chemical and biochemical properties of the prod- day, the butter is kneaded again to separate the water uct such as the synthesis of diacetyl processes and remaining in the structure as far as possible, to homog- increases in the formation of diacetyl. enize the added salt and to obtain a certain consis- In this study, the effect of butter storage in sheep’s tency for the filling operation. Water in the structure rumen on the productions of diacetyl and acetoin is removed by passing the kneaded butter through a was investigated. These compounds were determined spiral press before filling. The butter separated from and monitored by GC-MS. The effect of storage its water is carefully filled into the moistened karin time on their concentrations was also investigated. without allowing any air pockets to form. The butter filled into karin (rumen) is put on the market after it 2. EXPERIMENTAL is stored in cold storage (6–10 °C) for at least 15 days. The storage period of karın butter does not usually 2.1. Chemicals and samples exceed 3 months (Gökçe et al., 2010). The fact that the butter packaged in this way is Ultra-pure quality water (resistivity 18.2 MΩ·cm-1) more aromatic than butters packed in a commercial obtained with a reverse osmosis system (Human way has been confirmed by consumers (Adam, 1971; Corp., Seoul, Korea) was used for cleaning and Sag˘diç et al., 2002; Seçkin et al., 2005; Gökçe et al., other related solutions in all experiments. Aceton 2010; Gun and Simsek, 2011). There have been and n-hexane for the GC-MS analysis were obtain numerous articles dealing with the function of from Sigma-Aldrich (France, >99.9% HPLC grade) lactic acid bacteria in the improvement of flavor for the extraction and dilution solvent. Diacetyl compounds in dairy products. In cultured butter, (2,3-butanedione), acetoin (3-hydroxy-2-butanone) the main flavor compounds are usually assumed to and 2,3-pentadione as internal Standard (IS) were be diacetyl and acetaldehyde with an acidic back- purchased from Alfa aesar (Karlsruhe, Germany) ground provided largely by lactic acid (Green and and Merck (Holenbrunn, Germany), respectively. Manning, 1982; Seitz, 1990; Brito, 1990; Urbach, Stock standard solutions of 1 mg·mL-1 were pre- 1995; Escamilla-Hurtado et al., 2005). pared by diluting aceton:n-hexane (1:1, v/v) and then Diacetyl is a major flavor component of several storing at 4 °C. Fresh working solutions were pre- fermented dairy products including cultured butter pared by appropriate dilution with aceton:n-hexane. Grasas Aceites 65 (1), January–March 2014, e010. ISSN-L: 0017–3495 doi: http://dx.doi.org/10.3989/gya.074113 Simultatenous determination of diacetyl and acetoin in traditional turkish butter stored in sheep’s rumen (Karinyagi) • 3 Five butter samples were purchased from traditional 2.3. Extraction of diacetyl and acetoin from butter local markets in Denizli-Turkey. All the samples were samples used in the wet form without any treatment. The determination of diacetyl using the liquid- 2.2. Instrument and chromatographic conditions liquid extraction procedure with acetone as a solvent was reported by Macciola et al., (2008). The same Chromatographic analyses of aromatic com- procedure for the simultaneous extraction of diacetyl pounds were performed using a split/splitless injec- and acetoin from butter samples was used in this study. tor system (AOC 20s auto sampler with AOC 20i 2.0 g of butter sample were transferred in eppendorf auto injector) gas chromatograph (Shimadzu GC (15 mL) polyethylene tube.